This invention relates to laser processing machines and also to sewing machines with a laser processing function for performing processing such as cutting and engraving on a work by irradiating a work with a laser beam.
Japanese Patent Publication No. 6-33550 shows an embroidering machine with a plurality of sewing heads and laser heads each mounted on each sewing head. The embroidering machine further comprises an embroidering frame which can hold a cloth (or work). The embroidering frame is controlled for movement in X- and Y-axis directions according to drive data, while each laser head irradiates a laser beam to cut the cloth.
The above prior art embroidering machine has the following disadvantages.
(1) It is necessary to produce the drive data separately from a data for embroidering. The production of the drive data requires considerable man-hours. PA1 (2) It is necessary to secure a certain distance between each laser head and the cloth (or work) to facilitate such operations as replacement of cloth for the embroidering frame. This means that no means for protecting the operator from a laser beam is provided between the laser head and the cloth. PA1 (3) Each laser head requires an independent laser generator. The laser generator is relatively expensive, and an increase of the number of laser heads inevitably increases the cost. PA1 (4) The laser head is mounted on the sewing head, and the laser beam is irradiated in the close vicinity of the sewing head. This means that a throat plate covering a shuttle receives the laser beam at a position below the sewing head. This may result in scorching of a lower thread wound on a bobbin in the shuttle by the heat of the laser beam or in adverse effects on the throat plate or the shuttle by the heat of the laser beam. PA1 (5) When it is detected at the end of, or, during a cutting operation by a plurality of laser heads that an imperfect cut is produced by any of the laser heads, the cutting operation by that laser head has to be performed afresh. In such a case, it is necessary to return the work frame (or embroidering frame) by the frame return control to a point from which the cutting is to be performed afresh, and make cutting afresh from that point to the point from which the work frame has been returned. PA1 (6) In the conventional embroidering machine, power that is outputted from a plurality of laser tubes of a laser generator is made constant through feedback control according to a drive signal provided from a laser controller. However, the system for realizing the feedback control is expensive, thus inevitably leading to a cost increase of the embroidering machine. PA1 (7) When the work to be cut has a large thickness, or, in dependence on the material of the work or like conditions, it is necessary to increase the laser beam output. With an increased output of the laser beam, however, a cut (particularly edges) of work may excessively be burnt, thus resulting in an unclean finish. Besides, while it is necessary to set an increased laser beam output to cut a work having a large thickness as noted above, the output (or capacity) of the laser generator is limited. PA1 (8) For leading a laser beam from a laser generator to a laser head, a cylindrical guide is used to ensure safety. For redirecting a laser beam, a mirror is used. The redirection of the laser beam requires accuracy. This means that the mounting angle of the mirror has to be finely adjusted. This operation is very difficult and time-consuming. PA1 (9) Depending on laser processing, it is necessary to frequently adjust the focal point of the lenses. For example, this is required when laser processing two overlapped works to cut the upper work first and then cut the lower work, or when varying the width of scorching by the laser beam for providing a scorch pattern (or mark) on the surface of leather or like work.
In this case, however, with a laser head which has made a proper cutting, the laser beam is overlappingly irradiated onto the cut portions between the cutting restart point and the work frame return point. In this case, no problem arises so long as the cloth is perfectly cut by the laser beam. However, when only the upper one of two overlapped cloths is to be cut, the repeated cutting may result in the cutting or scorching of the lower cloth which should not be cut.
Heretofore, in such cases, the focal point of a lens has to be adjusted whenever it is necessary to do so by manually vertically moving a cylindrical member after loosening bolts. This operation is very time-consuming.